The present invention relates in general to nonlinear integrated and fiber optics and more specifically to completely optical switches and optical transistors and may be used in both fiberoptic and air-path optical communications, in optical logical schemes and in other fields, where all optical switching, amplification, control and modulation of optical radiation are needed.
Methods for switching are known in optical bistable devices with opposite-directional coupled waves, in particular, in Fabry-Perot resonators with a cubic-nonlinear medium (Felber F. S., Marburger J. H., Appl. Phys. Lett., 28, 731, 1976; Marburger J. H., Felber F. S., Phys. Rev., A 17, 335, 1878), and also in systems with a distributed coupling of waves (Winful H. G., Marburger J. H., Garmire E., Appl. Phys. Lett., 35, 379,1979; Winful H. G., Marburger J. H., Appl. Phys. Lett., 36, 613,1980).
Extensive opportunities for the creation of an optical switching, modulating and amplifying information signal are provided by a different class of systems with so-called unidirectional distributively coupled waves (UDCWs), if these waves propagate in a nonlinear medium. The methods and devices for optical switching, amplifying and modulating optical radiation based on the self-switching of the UDCWs was described for the first time in the papers: A. A. Maier, xe2x80x9cThe method of signal switching in tunnel coupled optical waveguidesxe2x80x9d, USSR Patent No. 1152397 (September 1982, publ. 1998). [Byull. Izobret. (46), 300 (1988)]; A. A. Maier, xe2x80x9cOptical transistors and bistable elements on the basis of nonlinear transmission of light in systems with unidirectional coupled wavesxe2x80x9d, Kvantovaya Elektron. 9, pp.2296-2302 (1982). [Sov. J. Quantum Electron., v.12, 1490 (1982)]; A. A. Maier, xe2x80x9cOn self-switching of light in a directional couplerxe2x80x9d, Kvantovaya Elektron. 11, pp.157-162 (1984). [Sov. J. Quantum Electron. v.11, p.101 (1984)]; A. A. Maier, xe2x80x9cSelf-switching of light in integrated opticsxe2x80x9d, Izv. Acad. Nauk SSSR, ser. Fis., v.48, 1441-1446 (1984). Later these methods and devices were extensively developed in the whole world.
In particular, in the known method for all-optical switching of radiation in tunnel-coupled optical waveguides A. A. Maier, xe2x80x9cThe method of signal switching in tunnel-coupled optical waveguidesxe2x80x9d, USSR Patent No. 1152397 (September 1982); Byull. Izobret. (46), 300 (1988)], a signal optical radiation with a variable small power and a pump optical radiation with a power more than threshold value are fed into cubic-nonlinear tunnel-coupled optical waveguides.
A method for switching and modulating UDCWs (P. Li. Kam Wa, P. N. Robson, J. S. Roberts, M. A. Pate, J. P. R. David,  less than  less than All-optical switching between modes of a GaAs/GaAlAs multiple quantum well waveguide) greater than  greater than , Appl.Phys.Lett. v.52, No. 24, 2013-2014, 1988.) is also known. The method consists of switching and modulating waves, propagating as different waveguide modes in a nonlinear-optical waveguide made on the basis of a layered semiconductor multiple quantum well (MQW) structure with alternating layers. The switching and modulating are achieved by changing the power transmission coefficient from one wave to another by changing the power at the input of the optical waveguide. Wavelengths are chosen to be close to an exiton resonance wavelength xcexr to provide for a maximum cubic-nonlinear coefficient of the waveguide.
With this method and device it is very difficult to fit the exiton resonance wavelength to the wavelength of pump optical radiation and/or signal optical radiation accurately. So it is very difficult to achieve a maximum nonlinear-optical coefficient, and therefore to decrease the threshold and critical powers of pump optical radiation to a sufficient degree. Besides, it is not possible to adjust (control, regulate) values of threshold and critical powers in order to chose a predetermined regime of operation of the device. The impossibility to adjust the values of threshold and critical powers leads to high demands on the stability in time of the pump optical radiation source, because even a small variation of pump optical radiation power can cause accidental radiation switching, i.e. in this case the probability of an accidental error in switching and modulation at the output is high. Besides, the method has the following significant shortcoming. If the exiton resonance wavelength is close to the wavelength of the pump and/or signal optical radiation then a large loss of the optical radiations takes place. In order to carry out the method a nonlinear-optical waveguide made on the basis of a nonlinear-optic semiconductor MQW wafer structure is used. Micro-objectives are placed at the input and output of the nonlinear-optical waveguide. Besides the shortcomings mentioned above, the device also has loss at the input and output due to shortcomings of collimating optics at the input and output, which ignore the shape (form) of the profile (section) of the nonlinear-optical waveguide. The complexity of placing and mounting the micro-objectives relative to the nonlinear-optical waveguide, and the large size of the device are also shortcomings of the method and the device.
One prior-art switching device (R. Jin, C. L. Chuang, H. M. Gibbs, S. W. Kohh, J. N. Polky, G. A. Pubans xe2x80x9cPicosecond all-optical switching in single-mode GaAs/AlGaAs strip-loaded nonlinear directional couplerxe2x80x9d, Appl. Phys. Lett., 53 [19], 1977, pp.1791-1792) also comprises nonlinear TCOWs, made on the basis of a layered nonliner-optic semiconductor MQW structure with alternate layers GaAs/AlGaAs. The wavelength of the input optical radiation is chosen close to the exiton resonance wavelength to provide a large cubic-nonlinear coefficient of the waveguides. Using this device it is possible to implement the method for switching, modulating, amplifying and controlling, consisting in feeding (launching) optical radiation into nonlinear TCOWs, switching coupled waves in the nonlinear-optical waveguides and separating coupled waves in neighboring optical waveguides at the output of the device.
It is also very difficult in this device and method to adjust the threshold and critical power. Besides, in the device the transmission of radiation through the nonlinear TCOWs is only 1%, this being due to the maximum of absorption at the exiton resonance wavelength. The small transmission and the impossibility to adjust the threshold and critical power; and the mode of operation restricts the field of using the device.
Besides the shortcomings mentioned above, this switching device has optical power losses because of defects of the collimating optics placed at the input and output of the device.
The low efficiency of the focusing and collimating elements at the input and output of the known devices is due to difficulties in precisely positioning and mounting the focusing and collimating elements (objectives) relative to the nonlinear-optical waveguides. Besides, the focusing and collimating elements in the known device do not take into account the asymmetry of the cross section of the nonlinear-optical waveguide(s).
Known methods for feeding light into an optical waveguide (for example, Inventor""s Certificate SU No. 1238569, 1984) do not provide possibility to control and check the efficiency of feeding optical radiation into the optical waveguide. This method does not provide for mounting focusing and collimating optical elements relative to the nonlinear-optical waveguide with precision, satisfying the high requirements in respect to the efficiency of feeding radiation into and/or feeding radiation out of the nonlinear-optical waveguide. This method cannot be used for mounting a semiconductor laser or laser module relative to the nonlinear-optical waveguide or nonlinear TCOWs either.
Uniting (joining) the aforesaid devices into a single chip is of great interest for devices processing optical signals, for example, for logical optical schemes, for optical computing devices and optical communications systems.
Known switching and logical schemes, for instance, described in the Hector E. Escobar  less than  less than All-optical switching systems near practical use greater than  greater than , Laser Focus World, October 1994, pp.135-141, paper have limited possibilities due to insufficient speed of operation.
Thus, the known methods and devices place limitations upon the value of the amplification factor of a variable signal.
A technical object of the invention is to significantly decrease the pump power at the input of the device with the possibility of increasing the gain (and sensitivity of the device to signal variation) and depth of switching, and also to provide the possibility for adjustment of threshold and critical powers and control of the differential amplification factor of a variable optical signal and the ratio of powers of coupled waves at the output of the device, and to achieve reliability of its operation and small sizes of the device.
A positive technical result of the present invention is also expressed in providing favorable conditions for creating an optical transistor, as well as devices based thereon.
A technical object of the invention is also to increase the speed of operation of the optical switching devices by use of quadratic-nonlinear-optical waveguide(s).
In first and second variants of a method of switching, amplification, controlling and modulation of optical radiation with use of a nonlinear-optical waveguide, made on the basis of a layered semiconductor MQW-type structure with alternating layers containing at least two hetero-transitions, the nonlinear-optical waveguide is made with an opportunity for propagation in it of two UDCWs, and the method including input of coherent optical radiation with power above the threshold power into the nonlinear-optical waveguide, or of pump optical radiation with power above the threshold power and at least one coherent signal optical radiation into the nonlinear-optical waveguide, interaction of UDCWs in the nonlinear-optical waveguide and separation of UDCWs at the output of the nonlinear-optical waveguide, the object is solved in that
a cubic and/or quadratic-nonlinear-optical waveguide is used,
the wavelength of radiation is chosen from a condition 0.5xcexrxe2x89xa6xcexxe2x89xa61.5xcexr, where xcexr is a wavelength of one-photon exiton resonance and/or two-photon exiton resonance and/or band-gap resonance and/or half-band-gap resonance of the semiconductor structure of the nonlinear-optical waveguide,
an electrical current is passed through the nonlinear-optical waveguide
a change of power, or polarization, or wavelength, or angle of input of continuous waves or signal optical radiation, or external electrical or magnetic field applied to the nonlinear-optical waveguide is made at the input of optical radiation or signal optical radiation into the nonlinear-optical waveguide.
In the third and fourth variants of the method of switching, amplification, controlling and modulation of optical radiation with use of a nonlinear-optical waveguide, made on the basis of a layered semiconductor MQW-type structure with alternating layers containing at least two hetero-transitions, and nonlinear-optical waveguide is made with an opportunity of propagation in it of two UDCWs, the method including input of polarized optical radiation with power above threshold power or polarized pump optical radiation with power above threshold power and of at least one polarized signal optical radiation into the nonlinear-optical waveguide, interaction of UDCWs of various polarizations in the nonlinear-optical waveguide and separation of the waves of various polarizations after output from the nonlinear-optical waveguide, the object is solved in that
the nonlinear-optical waveguide is made cubic- and/or quadratically-nonlinear,
the nonlinear-optical waveguide is made birefringent and/or optically active,
an electrical current is passed through the nonlinear-optical waveguide,
the wavelength of radiation is chosen from a condition 0.5xcexrxe2x89xa6xcexxe2x89xa61.5xcexr, where xcexr is a wavelength of one-photon exiton resonance and/or two-photon exiton resonance and/or band-gap resonance and/or half-band-gap resonance of the semiconductor structure of the nonlinear-optical waveguide,
a change of power, or polarization, or wavelength, or angle of input of continuous waves or signal optical radiation, or external electrical or magnetic field applied to the nonlinear-optical waveguide is implemented.
In the fifth and sixth variants of the method of switching, amplification, controlling and modulation of optical radiation with use of nonlinear-optical TCOWs, at least one of which is made on the basis of a semiconductor layered MQW-type structure with alternating layers containing at least two hetero-transitions, the method including input of optical radiation with power above threshold power or at least one signal optical radiation into at least one of the nonlinear-optical waveguides and pump optical radiation with power above threshold power into at least one nonlinear-optical waveguide, interaction of UDCWs in the nonlinear-optical TCOWs and separation and/or separation out of the optical waves after the output from the nonlinear-optical waveguides by feeding radiations from various waveguides and/or by means of a separator, the object is solved in that
nonlinear-optical waveguides are made as cubic and/or quadratic-nonlinear,
an electrical current is passed through at least one nonlinear-optical waveguide,
a wavelength of optical radiation is chosen from a condition 0.5xcexrxe2x89xa6xcexxe2x89xa61.5xcexr, where xcexr is a wavelength of one-photon exiton resonance and/or two-photon exiton resonance and/or band-gap resonance and/or half-band-gap resonance of the semiconductor structure of least one nonlinear-optical waveguide,
a change of power, and/or wavelength, and/or of polarization of input optical radiation, and/or of external electrical or magnetic field is implemented at the input of optical radiation in nonlinear-optical waveguide and applied to at least one nonlinear-optical waveguide.
Thus in all variants of the method the nonlinear-optical waveguide has a length which is not smaller than the length necessary for switching and/or transfer of at least 10% of power from one of the UDCWs into another, and the length of the nonlinear-optical waveguide, necessary for switching and/or transfer of at least 10% of power from one of said UDCWs into another, does not exeed the length, at which the power of the more strongly attenuated wave from the UDCWs decreases by 20 times or less.
In a more preferable embodiment of the suggested method and device, the length of the nonlinear-optical waveguide is not less than the length which is necessary for the switching and/or the transfer of at least 50% of power of one of the unidirectional distributively coupled waves to another one from the unidirectional distributively coupled waves, and the length of the nonlinear-optical waveguide which is necessary for the switching and/or the transfer at least 50% of the power of the one of the unidirectional distributively coupled waves to the other one from the unidirectional distributively coupled waves, does not exceed the length at which the power of the most attenuated wave from the unidirectional distributively coupled waves is attenuated by a factor of 10.
In an even more preferable embodiment of the suggested method and device, the length of the nonlinear-optical waveguide is not less than the length which is necessary for the switching and/or the transfer of at least 80% of power of one of the unidirectional distributively coupled waves to another one from the unidirectional distributively coupled waves, and the length of the nonlinear-optical waveguide which is necessary for the switching and/or the transfer at least 80% of the power of the one of the unidirectional distributively coupled waves to the other one from the unidirectional distributively coupled waves, does not exceed the length at which the power of the most attenuated wave from the unidirectional distributively coupled waves is attenuated by a factor of 10.
Thus, in special cases, the power of radiation or power of pump optical radiation is established on an input of the nonlinear-optical waveguide from a condition of maintenance of a given value of the differential factor of amplification and/or of a given ratio of powers and/or difference in phases of UDCWs at the output of stabilization of average power of continuous wave radiation or peak power of pulse radiation, or power of pump optical radiation.
In order to increase the differential gain and maintain linearity of the amplification in the case of cubic-nonlinear-optical waveguide or cubic-nonlinear TCOWs, as a rule the power of the fed continuous wave radiation, or peak power of the fed pulse radiation, or power of the pump optical radiation is chosen in the range from 0.4 PM to 3PM, where PMxe2x80x94the critical power given (consideration below); or mainlyxe2x80x94in the range from 0.6 PM to 1.5 PM, or even more preferably from 0.8 PM to 1.2 PM.
As a rule, the average power of radiation or the power of pump optical radiation, fed into the nonlinear-optical waveguide is stabilized.
In another special case pulse radiation, in particular solitons, is used as optical radiation or pump optical radiation and/or signal optical radiation.
Thus, in special cases, the temperature of the nonlinear-optical waveguide or at least one nonlinear-optical waveguide is set from a condition of choosing and maintaining the given value of threshold power and/or critical power and/or the differential factor of amplification and/or a given ratio of the powers and/or differences in phases of UDCWs at the output of the nonlinear-optical waveguide and/or differences in phases between them, and to stabilize the temperature of the nonlinear-optical waveguide.
In order to reduce threshold radiation intensity (by making the wavelengths of radiation and of the exiton resonance of the semiconductor structure closer) and to eliminate the influence of external temperature influences, the temperature of the nonlinear-optical waveguide or nonlinear TCOWs is adjusted and/or stabilized with a thermostat and/or at least one Peltier element, equipped with a regulator and/or a stabilizer of temperature.
In all variants of the method the power of pump optical radiation can be at least more than the power of signal optical radiation by a order of magnitude, or the powers of signal optical radiation and pump optical radiation can differ from their average value by no more than an order of magnitude.
As a rule, in order to exclude the existence of opposite-directional distributed coupled waves in the nonlinear-optical waveguide, at least one end face of the nonlinear-optical waveguide is covered with an AR coating.
As a rule, the wavelength xcex of the optical radiation is chosen from the conditions 0.9xcexrxe2x89xa6xcexxe2x89xa61.1xcexr.
In the variant of the method in which UDCWs having different polarizations (as a rule, having mutually orthogonal polarizations) are used, as a rule, the nonlinear-optical waveguide is made as birefringent and/or optically active. It should be mentioned that the MQW-type structure almost always has birefringence, however to reach a predetermined, sufficiently large birefringence, the difference in the refractive indexes of the layers should be sufficiently large; hence the value of  less than  less than x greater than  greater than  in such a structure as GaAs/AlxGa1xe2x88x92xAs should be sufficiently large, e.g. x greater than 0.1.
In special cases the UDCWs are waves of various wavelengths and/or various polarizations and/or various waveguide modes.
In special cases of all variants of the method, continuous waves of pulse radiation or pump optical radiation and/or signal optical radiation fed into the nonlinear-optical waveguide includes waves of two frequencies differing by a value larger than xcfx84xe2x88x921, where xcfx84 is a characteristic time of change of a parameter of the optical radiation. The parameter of the optical radiation is the power, the phase, the polarization, or the frequency of the optical radiation, the parameter of the signal optical radiation is the power, the phase, the polarization, or the frequency of the signal optical radiation. In particular, the carrying frequencies of signal optical radiation and pump optical radiation differ by a value larger than xcfx84xe2x88x921, where xcfx84 is a characteristic time of a change of a parameter of the signal optical radiation, in particular, pump optical radiation and signal optical radiation of various wavelengths are used. Then, after the output of the nonlinear-optical waveguide(s) the radiations of various wavelengths are separated or at least one of them is separated out by means of the separator.
In other special cases, optical radiation of linear or elliptic or circular polarization is used as coherent optical radiation fed into at least one nonlinear-optical waveguide or the pump optical radiation contains waves of at least two polarizations or two wavelengths or two waveguide modes.
In particular, pump optical radiation and signal optical radiation having identical or opposite circular polarization are used, or pump optical radiation and signal optical radiation having identical or various linear or elliptic polarization are used, thus at the output of the nonlinear-optical waveguides radiation of various polarizations are separated or at least one of them is separated by means of the separator.
In particular, pump optical radiation and signal optical radiation with linear or elliptic mutually orthogonal polarizations are used.
In a specific case, a difference in phases between the UDCWs having orthogonal polarization in the optical radiation fed into the nonlinear-optical waveguide is set up from the condition of maintenance of the given value of differential gain and/or the ratio of the UDCW powers at the output of the nonlinear-optical waveguide and/or the differences between the UDCW phases at the output.
In special cases, with one birefringent nonlinear-optical waveguide, a vector of an electrical field or an axis of an ellipse of polarization in optical radiation (or in signal and/or pump optical radiation) fed into the aforesaid nonlinear-optical waveguide is directed at an angle of 10xc2x0 less than xcex1 less than 80xc2x0 to a  less than  less than fast greater than  greater than  or  less than  less than slow greater than  greater than  axis of the aforesaid nonlinear birefringent optical waveguide, in particular, the vector of the electrical field or the axis of the ellipse of polarization in the optical radiation (or signal and/or pump optical radiation) entered into the aforesaid nonlinear-optical waveguide is directed at an angle of 10xc2x0 less than xcex1 less than 80xc2x0 or 30xc2x0 less than xcex1 less than 60xc2x0 or 45xc2x0 or xe2x88x9215 less than xcex1 less than 15xc2x0 to the  less than  less than fast greater than  greater than  or  less than  less than slow greater than  greater than  axis of the nonlinear-optical waveguide, either vector of the electrical field or the axis of the ellipse of polarization in optical radiation (or in the signal and/or the pump optical radiation) entered into the nonlinear-optical waveguide coincides with the  less than  less than fast greater than  greater than  or  less than  less than slow greater than  greater than  axis of the nonlinear-optical waveguide.
Thus, they orient the vector of the electrical field or the axis of the ellipse of polarization in optical radiation, entered into the nonlinear-optical waveguide relative to the  less than  less than fast greater than  greater than  or  less than  less than slow greater than  greater than  axis of the nonlinear-optical waveguide, by a turn of the optical elements of the nonlinear-optical module (connected by fiber-optic sockets and/or by optical connectors) around a longitudinal axis of the nonlinear optic module.
In special cases pump optical radiation and signal optical radiation with the same wavelength are used.
In special cases the pump optical radiation contains waves of at least two polarizations or two wavelengths or two waveguide modes.
As a rule, optical radiation of the semiconductor laser and/or of the laser module is used as coherent optical radiation, or pump optical radiation and/or signal optical radiation fed into the nonlinear-optical waveguide or nonlinear TCOWs. With this, in order to reduce, regulate or choose given threshold and critical powers and to increase or regulate differential gain (by increasing or regulating the nonlinear factor of the nonlinear-optical waveguide due to regulation of the degree of closeness to an exiton resonance of the wavelength of radiation of the laser) the temperature of radiating semiconductor structure of the laser and/or of the laser module is additionally adjusted and/or stabilized.
To increase the efficiency of feeding optical radiation into the nonlinear-optical waveguide and/or to increase the efficiency of feeding optical radiation out of the nonlinear-optical waveguide, the optical elements for the input/output of the optical radiation (hereinafter referred to as ,input/output elements,,) are mounted accordingly at the input and/or at the output of the nonlinear-optical waveguide, wherewith the input/output elements are mounted relative to the nonlinear-optical waveguide with a precision provided by their positioning (adjustment) with the aid of luminescent radiation of the nonlinear-optical waveguide, occurring when electrical current is passed through the nonlinear-optical waveguide.
As a rule, the input/output elements are made with asymmetry of the cross section of the nonlinear-optical waveguide. In other words the input/output elements are usually made with asymmetrical divergence of beam launching into the nonlinear-optical waveguide and/or asymmetrical divergence of the beam leaving the nonlinear-optical waveguide. That is why the efficiency of the input/output of optical radiation is very high ( the efficiency is about 70% and higher).
As a rule the input/output elements are mounted at the input and output ends of the nonlinear-optical waveguide, making a compact combined nonlinear-optic module.
In a specific preferred embodiment, the input/output elements are made as objectives; wherein, as a rule, the objective comprises a cylindrical lens and a gradan. In other words, to increase the efficiency of the input/output of optical radiation, the optical radiation is focused before the input and/or after passage through the nonlinear-optical waveguide the optical radiation is collimated by a cylindrical lens and/or gradan. As a rule, the surfaces of the cylindrical lenses and/or gradans are antireflection coated.
The positioning and/or mounting of the input and/or output elements, made as objectives, relative to the nonlinear-optical waveguide is accomplished until the formation of a collimated optical radiation beam outside (beyond) the objectives. As a rule the collimated optical radiation beam has cylindrical symmetry.
In another special preferred embodiment, the input/output elements are made as input and/or output optical waveguides (hereinafter referred to as input/output waveguides). In this case the feeding of optical radiation into the nonlinear-optical waveguide and/or the feeding of radiation out of the nonlinear-optical waveguide is carried out by the input and/or output waveguide. As a rule, a lens is made and/or gradan is mounted on the output and/or input end of the input and/or output optical waveguide. Usually the lens is made as a cylindrical lens or a parabolic lens or a conic lens. It should be noted that the output end of the input waveguide is adjoined to the input of the nonlinear-optical waveguide, and so the lens, by means of which the radiation is launched into the nonlinear-optical waveguide is formed on the output end of the input waveguide. Similarly the input end of the output optical waveguide is adjoined to the output of the nonlinear-optical waveguide, and so the lens, by means of which the radiation is fed out of the nonlinear-optical waveguide, is formed on the input end of the output optical waveguide. As a rule, the input and/or output end of the optical waveguides and/or gradans are antireflection coated.
The input and output waveguides are preferably surrounded by protective buffer covers. As a rule 3 mm and 0.9 mm buffer covers can be used.
The nonlinear-optical waveguide together with firmly mounted input/output elements at the ends of the nonlinear-optical waveguide can make up a nonlinear-optical module. Thus, a nonlinear-optical module comprises at least one nonlinear-optical waveguide and input/output elements. Besides, a nonlinear-optical module can comprise other optical elements: a separator of UDCWs, an optical polarizer, an optical isolator, laser, phase compensator, polarization controller and etc., optically and firmly mechanically connected to each other; and other elements: a thermoelectric Peltier element, temperature sensor, mountings elements and other subsidiary elements firmly connected to each other.
In order to provide the possibility for modulation of optical radiation by an electric current on the basis of Faraday effect, the input waveguide is made from a magneto-optic material and is placed in a solenoid, through which a variable electrical current modulating the polarization of the optical radiation is passed, or is made as an electrooptical rotator of a plane of polarization; or the input waveguide contains a Y-mixer, into one input input branch of which the signal optical radiation is fed, and into the other input branchxe2x80x94the pump optical radiation is fed wherein, the input branch, into which the signal optical radiation is fed, is made from a magneto-optic material and is placed in a solenoid, through which the variable electric current modulating polarization of signal optical radiation is passed, or is made as an electrooptical rotator of a plane of polarization.
As a rule, in all variants of the method, a constant electric current from 0.5 mA up to 10 mA is carried (passed) across the nonlinear-optical waveguide, wherein the current spread from an average value over time does not exceed 0.1 mA.
In that specific case, with the purpose of providing the possibility of controllability (in particular, for rejection of noise and jamming in optical communication lines) the electric current is passed through the nonlinear-optical waveguide in given intervals of time.
In another special case for elimination of atmosphere fluctuations, noise and jamming dependences on time of powers of the UDCWs, separated after the output of the nonlinear-optical waveguide, are compared and their amplified opposite-modulation in powers is selected out by means of a correlator and/or differential amplifier.
It is preferred for elimination of the return influence of reflected radiation that an optical isolator be mounted before the input of the nonlinear-optical waveguide and/or after its output. In particular, the optical isolator is made as a waveguide optical isolator, e.g., fiber-optic isolator.
In all variants of the method the separation of UDCWs after the output of the nonlinear-optical waveguide is executed by the separation of waves of various polarizations and/or of various wavelengths, and/or of waves in different TCOWs, and/or of various waveguide modes or by the separation out of one wave of predetermined polarization, or predetermined wavelength, or from one of TCOWs, or predetermined waveguide mode.
In the case of using UDCWs of various polarizations, their separation after the output of the nonlinear-optical waveguide is carried out by a polarizer, which, as a rule, is made as a polaroid, or a polarizing prism, or a birefringent prism, or a directional coupler, separating polarization, or as a polarizer on the basis of a single optical waveguide.
In special cases, in order to reduce the requirements in respect to stability of a source of pump optical radiation, pump optical radiation and/or at least one signal optical radiation with various wavelengths is chosen, and the wavelength of the exiton resonance xcexr in the semiconductor MQW-type structure of the nonlinear-optical waveguide is set by regulation of its temperature, and/or the wavelength of laser radiation is set by regulation of the temperature of the radiating semiconductor structure of the laser in such manner that the difference between the wavelength of signal optical radiation(s) and the wavelength of the exiton resonance in the semiconductor MQW-type structure of the nonlinear-optical waveguide is less than the difference between the wavelength of the pump optical radiation and the wavelength of the exiton resonance in the semiconductor MQW-type structure of the nonlinear-optical waveguide.
In special cases, in order to reduce the requirements in respect to stability of a source of pump optical radiation, pump optical radiation and/or at least one signal optical radiation with various wavelengths is chosen, and the wavelength of the exiton resonance xcexr in the semiconductor MQW-type structure of the nonlinear-optical waveguide is set by regulation of its temperature, and/or the wavelength of laser radiation is set by regulation of the temperature of the radiating semiconductor structure of the laser in such manner that the difference between the wavelength of signal optical radiation(s) and the wavelength of the exiton resonance in the semiconductor MQW-type structure of the nonlinear-optical waveguide is more than the difference between the wavelength of the pump optical radiation and the wavelength of the exiton resonance in the semiconductor MQW-type structure of the nonlinear-optical waveguide.
In the seventh variant of the method of switching, amplification, controlling and modulation of optical radiation carried out with the use of at least one nonlinear-optical waveguide, made on the basis of a layered semiconductor structure such as MQW with alternating layers containing at least two hetero-transitions, and the nonlinear-optical waveguide is made with an opportunity for propagation therein of opposite-directional coupled waves, the method including feeding at least one optical radiation with power above the threshold value into the nonlinear-optical waveguide, switching power between the coupled waves at the output and input of the nonlinear-optical waveguide(s) effected by changing at least one of the parameters of optical radiation at the input, the object is solved by
feeding optical radiation with at least one changeable parameter and power above the threshold power or pump optical radiation with power above the threshold power and at least one signal optical radiation with at least one changeable parameter,
using an optical waveguide or an optical waveguide having cubic and/or quadratic nonlinearity,
passing an electrical current through the nonlinear-optical waveguide(s),
choosing a wavelength of optical radiation with a changeable parameter, or pump optical radiation, or signal optical radiation, or pump and signal-optical radiation, from the condition 0.5xcexrxe2x89xa6xcexxe2x89xa61.5xcexr, where xcexr is the wavelength of one-photon exiton resonance or two-photon exiton resonance and/or band-gap resonance or half-band-gap resonance of the semiconductor MQW-type structure of the nonlinear-optical waveguide,
changing the power and/or phase(s) and/or polarization of the entered optical radiation, and/or wavelength and/or angle of input of the entered optical radiation, and/or an external electrical or magnetic field applied to the nonlinear-optical waveguide.
In a specific case, the average power of optical radiation with a changeable parameter, or the power of pump optical radiation, entering the nonlinear-optical waveguide(s) at the input waveguide is set from the condition of maintenance of the given value of the differential factor of amplification and/or of the given ratio of powers of the coupled waves at the output and the input of the nonlinear-optical waveguide(s).
As a rule, the average power of optical continuous wave radiation with a changeable parameter or the peak power of pulse optical radiation or the power of pump optical radiation is stabilized.
In another special case, pump optical radiation is applied as pulses, for example, as solitons.
In a specific case, the temperature of at least one nonlinear-optical waveguide is set from the condition of maintenance of a given value of the threshold power and/or of the differential factor of amplification and/or the ratio of the powers of the coupled waves at the output and input ends of the nonlinear-optical waveguide(s), and the temperature of the nonlinear-optical waveguide(s) is stabilized.
In order to decrease threshold intensity of the optical radiation (due to rapproachement of the wavelengths of the radiation and the exiton resonance of the MQW-type structure) and eliminate the influence of external temperature, the temperature of the nonlinear-optical waveguide and the said MQW-type structure are set and/or regulated and/or stabilized by at least one Peltier element and a temperature sensor and/or thermostat.
In a specific case, the wavelength xcex of the optical radiation with changeable parameter or the pump optical radiation or/and the signal optical radiation are chosen from the condition 0.9xcexrxe2x89xa6xcexxe2x89xa61.1xcexr.
In special cases, the power of the opposite-directional coupled waves of various frequencies is switched, thus the switching of power is done between the coupled waves of various frequencies and/or of opposite directions.
As a rule, a constant electrical current in the range from 0.5 mA up to 10 mA is passed across the nonlinear-optical waveguide(s), the current spread from the average value over time not exceeding 0.1 mA.
With the aim of achieving the possibility of controlling the gain (in particular, to eliminate noise and jamming in optical communication lines), an electrical current is passed through the waveguide in given intervals of time.
In order to eliminate the influence of radiation reflected from the ends of waveguides on a source of radiation or other optical elements located before the waveguides, and also to eliminate the influence of the reflected radiation on the nonlinear-optical waveguide, an optical isolator is mounted before the input of the nonlinear-optical waveguide and/or after its output. In particular, the optical isolator is made as a waveguide optical isolator, e.g., a fiber-optic isolator.
As a rule, radiation of a semiconductor laser and/or of a laser module is used as optical continuous waves or pulse radiation and/or pump optical radiation and/or signal optical radiation with the temperature of radiating semiconductor structure of the laser and/or of the laser module being adjusted and/or stabilized.
In a specific case, in order to reduce the requirements for stabilizatino of a source of pump optical radiation, pump optical radiation and/or at least one signal optical radiation with various wavelengths is chosen, and the resonance wavelength xcexr in the semiconductor structure of the nonlinear-optical waveguide is set by adjustment of its temperature, and/or the radiation wavelength of the laser is set by adjustment of the temperature of the radiating semiconductor structure of the laser in such a way that the difference between the wavelengths of signal optical radiation and of the exiton resonance of the semiconductor structure of the nonlinear-optical waveguide is less than the difference between the wavelengths of pump optical radiation and of the exiton resonance in the semiconductor structure of the nonlinear-optical waveguide.
In another special case, in order to reduce the threshold power, pump optical radiation and/or signal optical radiation with various wavelengths is chosen, and the resonance wavelength xcexr in the semiconductor structure of the nonlinear-optical waveguide is set by adjustment of its temperature, and/or the laser radiation wavelength is set by adjustment of the temperature of the radiating semiconductor structure of the laser in such way that the difference between the wavelengths of signal optical radiation and of the resonance in the semiconductor structure nonlinear-optical waveguide is more than the difference between the wavelengths of pump optical radiation and of the resonance of the semiconductor structure of the nonlinear-optical waveguide.
In that specific case, in order to increase the efficiency of input/output of the radiation before feeding radiation into at least one nonlinear-optical waveguide, the radiation is focused and/or after its passage through the nonlinear-optical waveguide(s) the optical radiation is collimated with the help of a cylindrical lens and/or gradan; as a rule, the surfaces of the cylindrical lenses and/or gradans are covered with an AR coating.
In the other special case, in order to increase the efficiency of input/output of optical radiation, the feeding of radiation into the nonlinear-optical waveguide(s) and/or the feeding of radiation from a nonlinear-optical waveguide(s) is carried out by means of a corresponding input and/or output waveguide; as a rule, a cylindrical lens and/or parabolic lens and/or conic lens is made or a gradan is mounted at the output and/or input end of the input and/or output optical waveguide; as a rule, the input and/or the output end of the waveguide(s) and/or gradan(s) are antireflection coated.
In the first and second variants of the device for switching, amplification, controlling and modulation of optical radiation containing a nonlinear-optical waveguide, made on the basis of layered semiconductor structure such as MQW with alternating layers containing at least two hetero-transitions, and the nonlinear-optical waveguide is made with an opportunity for propagation therein of at least two UDCWs, and also the device contains optical elements of an input/output located accordingly at the input and/or the output of the nonlinear-optical waveguide, and a separator of UDCWs at the output of the device, the object is solved in that
the nonlinear-optical waveguide is made as cubic and/or quadratic nonlinear,
the nonlinear-optical waveguide is provided with contacts for passage of an electric current through it,
a wavelength xcexr of one-photon and/or two-photon exiton resonance and/or band-gap resonance and/or half-band-gap resonance in the semiconductor structure of at least one nonlinear-optical waveguide satisfies the inequality 0.5xcexrxe2x89xa6xcexxe2x89xa61.5xcexr, where xcex is the wavelength of at least one optical radiation fed into the nonlinear-optical waveguide,
the input/output elements are mounted relative to the nonlinear-optical waveguide with a precision provided by their positioning with use of luminescent radiation of the nonlinear-optical waveguide, the luminescent radiation occurring when the electric current is passed through the nonlinear-optical waveguide,
the device further contains at least one Peltier element, one side of which is in thermal contact with the nonlinear-optical waveguide and with at least one temperature sensor.
In the second variant of embodiment of the device for switching, amplification, controlling and modulation of optical radiation, comprising two nonlinear TCOWs, at least one of which is made on the basis of layered semiconductor structure such as MQW with alternating layers, containing at least two hetero-transition, and optical elements of an input/output located accordingly at the input and/or the output of at least one of the nonlinear TCOWs, the object is solved in that
the nonlinear TCOWs are made as cubic and/or quadratic-nonlinear,
at least one nonlinear-optical waveguide is supplied with contacts for passage of electric current through it,
a wavelength of one-photon and/or two-photon exiton resonance xcexr of the semiconductor structure of at least one nonlinear-optical waveguide satisfies the inequality 0.5xcexr,xe2x89xa6xcexxe2x89xa61.5xcexr, where xcex is the wavelength of at least one optical radiation fed into the nonlinear TCOWs,
the input/output elements are mounted relative to the nonlinear-optical waveguides with a precision provided by their positioning with use of luminescent radiation of the nonlinear-optical waveguides, occurring when electrical current is passed through them,
the device further contains at least one Peltier element, one side of which is in thermal contact with at least one nonlinear-optical waveguide and with at least one temperature sensor,
a length of said nonlinear tunnel-coupled optical waveguides is not less than the length, which is necessary for switching or transfer of at least 10% of power from one of said nonlinear tunnel-coupled optical waveguides to the other one from said nonlinear tunnel-coupled optical waveguides, thereto the length of said nonlinear tunnel-coupled optical waveguides, which is necessary for switching or transferring of at least 10% of the power from one of the nonlinear tunnel-coupled optical waveguides to the other one of the nonlinear tunnel-coupled optical waveguides, does not exceed the length at which the power of the most attenuated wave from said unidirectional distributively coupled waves is attenuated by a factor of 20 or less.
In a more preferable embodiment a length of said nonlinear tunnel-coupled optical waveguides is not less than the length, which is necessary for switching or transfer of at least 50% of power from one of the nonlinear tunnel-coupled optical waveguides to the other one of the nonlinear tunnel-coupled optical waveguides, wherewith the length of said nonlinear tunnel-coupled optical waveguides, which is necessary for the switching or transfer of at least 50% of the power from one of said nonlinear tunnel-coupled optical waveguides to the other one of the nonlinear tunnel-coupled optical waveguides, does not exceed the length, at which the power of the most attenuated wave among the unidirectional distributively coupled waves is attenuated by a factor of 10.
As a rule, at least one temperature sensor and at least one Peltier element are electrically connected to a temperature regulator and/or to a temperature stabilizer.
As a rule the end faces of nonlinear-optical waveguide(s) have AR coatings.
In particular, the AR coatings at the ends of a nonlinear-optical waveguide are made to decrease the reflection factor of optical radiation from input and/or output ends up to a value of no more than 1%.
As a rule, the device contains a source of current (which is usually made as a controller and stabilizer of the current) connected to electrical contacts of the nonlinear-optical waveguide; in particular, the source of current is a source of constant current supplying electric current across the nonlinear-optical waveguide with values from 0.5 mA to 10 mA in operation, wherewith the current spread from an average value in time does not exceed 0.1 mA.
In one specific case, with the purpose to control the gain (in particular, for the elimination of noise and jamming in optic communication lines), the source of constant current is supplied with a high-speed switch.
In another special case, a correlator of optical waves and/or differential amplifier is set after the separator of UDCWs at the output of the device.
In particular cases, the aforesaid semiconductor MQW-type structure is made as alternating layers GaAs/AlxGa1xe2x88x92xAs, or InxGa1xe2x88x92xAs/InP, or In1xe2x88x92xxe2x80x2Gaxxe2x80x2Asyxe2x80x2P1xe2x88x92yxe2x80x2, Y, where xxe2x89xa0xxe2x80x2 and/or yxe2x89xa0yxe2x80x2, or CdSe1xe2x88x92xSx/CdSe or InAs1xe2x88x92xSbx/InAs, or PbSxSe1xe2x88x92x/PbSe, or GexSi1xe2x88x92x/Si or alternating layers of other semiconductor materials.
In the case of using TCOWs, as a rule, both nonlinear TCOWs are made on the basis of a united semiconductor layered MQW-type structure with alternating layers.
In special cases, when the device is used for switching, amplification, controlling and modulation of optical radiation, the separator of the UDCWs at the output of the device is made as the separator of waves with various polarizations; wherewith a polarizer can be mounted before the nonlinear-optical waveguide.
The function of a polarizer can be carried out by an optical isolator mounted before the input of the nonlinear-optical waveguide. The optical isolator also eliminates the return influence of radiation, reflected from waveguide ends and other optical elements, on the source of optical radiation or other optical elements placed before the nonlinear-optical waveguide. In particular, the optical isolator is made as a waveguide optical isolator, e.g., as a fiber-optic isolator.
In special cases, the separator of waves of various polarizations and/or the polarizer, mounted before the nonlinear-optical waveguide or nonlinear TCOWs, is made as a polaroid, or a polarizing prism, or a birefringent prism, or a directional coupler, separating waves of different polarizations, or a polarizer on the basis of a single optical waveguide.
The function of the separator of optical waves with various polarizations can be carried out by the nonlinear-optical waveguide as such or by an optical isolator mounted after the output of the nonlinear-optical waveguide. In the latter case the influence of the reflected radiation on the nonlinear-optical waveguide is eliminated. In particular. the optical isolator is made as a waveguide optical isolator, e.g., a fiber-optic isolator.
In special cases, when optical radiation of various wavelengths is used, the separator of the UDCWs at the output of the device is made as a separator of waves of various wavelengths.
In this case the separator of waves of various wavelengths is made as a dispersive element or a frequency filter or a directional coupler.
In special cases, when the optical radiation of various optical waveguide modes is used, the separator is made as a diaphragm for separation of the various waveguide modes or as a waveguide separator of the modes.
In the case of use of nonlinear TCOWs, as a rule, the TCOWs as such operate as a separator of coupled waves in the neighboring waveguides: one of the UDCWs leaves the zero waveguide, and another leaves the first waveguide.
Sometimes, the nonlinear TCOWs can be made as TCOWs separating radiation of various polarizations and/or of various wavelengths and/or of various waveguide modes at the output of the device.
To provide the possibility for orientation of xe2x80x9cfastxe2x80x9d and xe2x80x9cslowxe2x80x9d axes of the nonlinear-optical waveguide relative to a vector of an electrical field of linearly polarized optical radiation or axes of an ellipse of polarization of optical radiation, the semiconductor laser and/or laser module and/or nonlinear-optical waveguide with optical elements for the input and output of radiation and/or the separator of the UDCWs at the output of the device and/or the polarizer mounted at the input of the nonlinear-optical waveguide and/or the optical isolator are connected among themselves by fiber-optic sockets and fiber-optic connectors ensuring an opportunity for the aforementioned elements relative to each other around the optical axis of the device. Wherewith the optical isolator is made as a waveguide optical isolator, as a rule, in the form of a fiber-optic isolator.
As a rule, the nonlinear-optical waveguide is oriented relative to a vector of polarization of optical radiation which has entered the nonlinear-optical waveguide, in such a way that the vectors of an electric field of the linearly polarized optical radiation which has entered the nonlinear-optical waveguide, or the axis of an ellipse of polarization of the elliptically polarized optical radiation, which has entered the nonlinear-optical waveguide, are set at an angle of 10xc2x0 less than xcex1 less than 80xc2x0 to the xe2x80x9c less than  less than fastxe2x80x9d and/or  less than  less than slow greater than  greater than  axes in the birefringent nonlinear-optical waveguide, in a specific casexe2x80x94at an angle of 40xc2x0 less than xcex1 less than 50xc2x0, in particularxe2x80x94at an angle of 45xc2x0. In another special case the nonlinear-optical waveguide is oriented relative to a vector of polarization of optical radiation, which has entered the nonlinear-optical waveguide, in such a way that the vectors of an electrical field of the linearly polarized optical radiation which has entered the nonlinear-optical waveguide, or the axis of an ellipse of polarization of the elliptically polarized optical radiation which has entered the nonlinear-optical waveguide is directed at an angle xe2x88x9210xc2x0 less than xcex1 less than 10xc2x0 to the  less than  less than fast greater than  greater than  and/or  less than  less than slow greater than  greater than  axes of the nonlinear-optical waveguide. In particular, the vector of an electrical field of the linearly polarized optical radiation which has entered the nonlinear-optical waveguide or the axis of an ellipse of polarization of the elliptically polarized optical radiation which has entered the nonlinear-optical waveguide coincides with the  less than  less than fast greater than  greater than  and/or  less than  less than slow greater than  greater than  axis of the nonlinear-optical waveguide.
In particular, the opportunity for a relative turn of the elements is provided by use of fiber-optic sockets and connectors such as FC/PC.
Let it be noted that if UDCWs are UDCWs having orthogonal polarization, then the angular position of the separator, which in this case is made as a polarizer (e.g. polaroid), is determined by two UDCWs which are under consideration. So the opportunity for a relative turn (or rotation) of the separator relative to the nonlinear-optical waveguide should be provided. It can be provided by use of fiber-optic sockets and connectors such as FC/PC.
In a specific case, to provide the possibility for input into the nonlinear-optical waveguide of two and more optical radiations (pump optical radiation and at least one signal optical radiation) the input waveguide is made as at least one Y-mixer or directional coupler.
Thus, to provide the possibility for modulation of optical radiation by an electrical current on the basis of the Faraday effect, one input branch of the optical waveguide mixer is made from magneto-optic material and is surrounded by solenoid or is made as an electrooptical rotator of a plane of polarization.
In another special case, the device additionally contains a mixer of pump optical radiation and at least one signal optical radiation mounted at the input of the device; in particular, the mixer is made as a waveguide mixer, in which the output branch is the input waveguide.
As a rule, the input and/or output elements are connected to the nonlinear-optical waveguide by glue, or by splice, or by welding, or by soldering, or by means of a tiny mechanical connector.
In order to set a given difference in the phases of the UDCWs, a phase compensator, or phase controller is mounted at the input and/or at the output of the nonlinear-optical waveguide before and/or after the nonlinear-optical waveguide, in particular, the phase compensator or phase controller is made as an optical waveguide.
As a rule, the device additionally contains at least one semiconductor laser and/or laser module with modulated output radiation power, and/or a laser module as a source of pump optical radiation, the power of which exceeds the threshold power of the semiconductor laser and/or laser module with modulated output radiation power. The semiconductor laser and/or the laser module is mounted relative to the nonlinear-optical waveguide with a precision provided by its positioning with the aid of luminescent emission of the nonlinear-optical waveguide, occurring when electric current is passed across it, and/or by control of a change of optical radiation power, transmitted through the nonlinear-optical waveguide, when the electric current (with a value less than that required for the positioning) across it is switching on and/or switching off; in particular, a semiconductor laser and/or laser module with a spectrum-line width not exceeding 20 xc3x85 is used.
Wherewith, the semiconductor laser and/or the laser module is connected to at least one nonlinear-optical waveguide by means of an input element made as an input waveguide.
For stabilization of the radiation wavelength (i.e. frequency) and/or to obtain a one-frequency mode of generation, the semiconductor laser and/or the laser module is made with an external resonator and/or includes a dispersive element.
In a specific case, a periodic grating which is a partially or completely reflecting Bragg reflector is used as at least one mirror of the external resonator.
In particular, the mirror of the external resonator (of the semiconductor laser and/or laser module including the semiconductor laser and optical waveguide) is made as a periodic grating of refractive index in an optical waveguide made in the form of a fiber-optic waveguide contiguous to the laser; or the mirror is made as a corrugation on a surface of the optical waveguide contiguous to the laser.
In another special case, the dispersive element is made as a diffracted grating.
In order to decrease threshold radiation intensity and eliminate the influence of external temperature, the device additionally contains at least one Peltier element, one side of which is in thermal contact with the nonlinear-optical waveguide and with at least one temperature sensor.
Wherewith at least one temperature sensor and at least one Peltier element are electrically connected to a temperature controller (driver) and/or to a temperature stabilizer.
Wherewith a thermistor, and/or a thermocouple and/or a sensor in the form of an integrated circuit is used as the temperature sensor.
In a specific case, the device contains a radiator for the removal of heat, placed in thermal contact with one ( less than  less than hot greater than  greater than ) side of Peltier element.
In order to eliminate the influence of external temperature, the radiating semiconductor structure of the laser is additionally provided with at least one thermoelectric Peltier element, a side of which is in thermal contact with the radiating semiconductor structure, and with at least one temperature sensor, wherewith at least one temperature sensor and at least one thermoelectric Peltier element are electrically connected to a controller and/or stabilizer of the temperature.
The device for switching, amplification, controlling and modulation of optical radiation is easily united with similar devices, i.e. it is easily ,cloned,,. To do this it additionally contains at least one device similar to the first one, and at least one input element of each subsequent device is connected optically with at least one output element of the preceding device.
Wherewith, in a specific case, the input/output elements of the separate devices are made as a united optical waveguide or as joined optical waveguides.
In a third variant of the device for switching, amplification, controlling and modulation of optical radiation containing at least one nonlinear-optical waveguide, made on the basis of a layered nonlinear-optical semiconductor MQW-type structure with alternating layers containing at least two hetero-transitions, the device is made with the possibility for propagation in the nonlinear-optical waveguide of at least two opposite-directional coupled waves, the object is achieved in that the nonlinear-optical waveguides are quadratic- and/or cubic- nonlinear, at least one nonlinear-optical waveguide is provided with contacts for passage of an electric current through them,
the wavelength xcexr of one-photon and/or two-photon exiton resonance in the semiconductor structure of at least one nonlinear-optical waveguide satisfies the relationship 0.5xcexrxe2x89xa6xcexxe2x89xa61.5xcexr, where xcex is the wavelength of optical radiation,
input and/or output elements are mounted relative to the nonlinear-optical waveguide(s) with a precision provided by their positioning with the aid of luminescent emission of the nonlinear-optical waveguide(s), occurring when the electric current is passed through it (them),
the device additionally contains at least one Peltier element, one side of which is in thermal contact with at least one nonlinear-optical waveguide, and with at least one temperature sensor.
In particular cases, the semiconductor structure is made as alternating layers GaAs/AlxGa1xe2x88x92xAs, or InxGa1xe2x88x92xAs/InP, or In1xe2x88x92yxe2x80x2Gaxxe2x80x2Asyxe2x80x2P1xe2x88x92yxe2x80x2, where xxe2x89xa0xxe2x80x2 and/or yxe2x89xa0yxe2x80x2, or CdSe1xe2x88x92xAx/CdSe or InAs1xe2x88x92xSbx/InAs, or PbSxSe1xe2x88x92x/PbSe, or GexSi1xe2x88x92x/Si or alternating layers of other semiconductor materials.
In special cases, as the temperature sensor, a thermistor, and/or a thermocouple is used and/or the sensor is an integrated circuit.
As a rule, at least one sensor and at least one Peltier element are electrically connected to the temperature controller (regulator) and/or the temperature stabilizer.
In a specific case, the device contains a radiator for the removal heat, placed in thermal contact with at least one Peltier element.
As a rule, the device additionally contains an electric current source, electrically connected to the electrical contacts of the nonlinear-optical waveguide.
As a rule, a current through the nonlinear-optical waveguide passes in a direction perpendicular to the layers of the semiconductor structure.
As a rule, the electric current source is a precision direct current source providing electric current across the nonlinear-optical waveguide in operation with values from 0.5 mA to 10 mA, wherewith the current spread from the average value in time does not exceed 0.1 mA.
As a rule, the contacts for passage of electric current through the nonlinear-optical waveguide are electrically connected to a driver (regulator, controller) and/or stabilizer of the current.
In special cases, the device additionally contains at least one semiconductor laser and/or laser module with modulated output radiation power, and/or laser module as a source of pump optical radiation, the power of which exceeds threshold power of the semiconductor laser and/or the laser module with modulated output radiation power; wherewith the semiconductor laser and/or laser module is mounted relative to the nonlinear-optical waveguide with a precision provided by its positioning by luminescent emission of the nonlinear-optical waveguide, occurring when an electric current flows across it, and/or by the check of a change of optical radiation power, transmitted through the nonlinear-optical waveguide, by switching the electric current (with a value less than that required for the positioning) flowing across it on and/or off; in particular, a semiconductor laser and/or laser module with a spectrum-line width not exceeding 20 xc3x85 is used.
In order to eliminate temperature influences and to stabilize the frequency of the laser radiation, the radiating semiconductor structure of the laser and/or of the laser module is additionally provided with at least one Peltier element, one side of which is in thermal contact with the radiating laser semiconductor structure and with at least one temperature sensor, wherewith at least one temperature sensor and at least one Peltier element are electrically connected to a temperature controller and/or stabilizer of temperature.
In special cases, the semiconductor laser and/or laser module is used with a spectrum-line width of radiation, which is not more than 20 xc3x85.
In order to stabilize the wavelength of radiation and/or maintain the one-frequency mode of generation, the semiconductor laser and/or laser module is made with an external resonator and/or includes a dispersive element.
In a specific case, a periodic grating which is a partially or completely reflecting Bragg reflector is used as at least one mirror of the external resonator.
In particular, the mirror of the external resonator of the semiconductor laser and/or of a laser module including the semiconductor laser and waveguide is made as a periodic grating of refraction index contiguous to the laser waveguide, made as a fiber-optic waveguide, or as a corrugation on a surface of an optical waveguide, contiguous to the laser.
In one special case, at the ends of the nonlinear-optical waveguide, the mirrors are made with formation of a Fabry-Perot element.
In particular, the mirrors are made by means of a natural cleave, or by coating reflected coatings, or as periodic gratings which are Bragg reflectors.
In another special case, the periodic grating in the nonlinear-optical waveguide is made with formation of an optical bistable element with distributed feedback.
In special cases, the nonlinear-optical waveguide is birefringent and/or magneto-optic and/or electrooptical and/or acouso-optic.
In a third special case, the device additionally contains a second nonlinear-optical waveguide, and both nonlinear waveguides are TCOWs.
In one special case, in order to increase the radiation input/output efficiency the input and/or output elements are made as objectives consisting of a cylindrical lens and/or gradan; as a rule, the surfaces of the cylindrical lenses and/or gradans are antireflection coated.
In another special case, the input and/or output elements are made as input and/or output waveguides. As a rule, a cylindrical lens and/or parabolic lens and/or conic lens is formed and/or gradan is mounted on the output and/or input face of the said input and/or output optical waveguide. As a rule, the input and/or output faces of the optical waveguides and/or gradans are antireflection coated.
In special cases, the semiconductor laser is connected to at least one nonlinear-optical waveguide by means of an input element with formation of a united optical waveguide.
The object is also achieved in a method for assembly of a nonlinear-optical module comprising positioning, mounting and connection of at least one nonlinear-optical waveguide, made on the basis of a layered nonlinear-optical semiconductor structure such as MQW with alternating layers containing at least two hetero-transition, and input and/or output elements for the input and/or output of optical radiation, the method comprising mounting and positioning input and/or output elements relative to the nonlinear-optical waveguide, and mounting and positioning the input and/or output elements relative to the nonlinear-optical waveguide, provided by contacts for the flow of an electrical current through the nonlinear-optical waveguide, are carried out by luminescent radiation of the nonlinear-optical waveguide, occurring when electric current flows through it. The nonlinear-optical module comprises at least one nonlinear-optical waveguide and input/output elements.
In special cases, the semiconductor laser or the laser module is additionally mounted at least at one input of the nonlinear-optical module, the laser or the laser module with the nonlinear-optical module is positioned and connected, and thus the positioning of the laser or the laser module is carried out by changing the mutual position of the laser or laser module and the nonlinear-optical module until there is coincidence of the laser or of the laser module radiation beam and the luminescent radiation beam of the nonlinear-optical waveguide. When the luminescent radiation beam occurs by passing electric current across the nonlinear-optical waveguide; the coincidence must take place before and/or after the nonlinear-optical module.
When carrying out the positioning (adjusment) a current of, as a rule, more than 30 mA flows across the nonlinear-optical waveguide.
As a rule, the precision of positioning the laser or laser module relative to the nonlinear-optical module is additionally controlled by comparing the power of the optical radiation of the laser, or of the laser module, transmitted through the nonlinear-optical module in the absence of the electric current across the nonlinear-optical waveguide and when there is current across it. For this control current of an order of magnitude less than the current providing the aforesaid luminescent radiation of the nonlinear-optical waveguide is usually used.
Wherewith, the current, across the nonlinear-optical waveguide is, as a rule, from 1 up to 10 mA.
In the case of association of several optical modules (so called ( less than  less than cloning greater than  greater than ) another other (i.e. the second) similar nonlinear-optical module is additionally positioned and mounted at the output of the first nonlinear-optical module, wherewith the second similar nonlinear-optical module is adjusted relative to the first nonlinear-optical module by means of luminescent radiation of the nonlinear-optical waveguide of the first and/or the second nonlinear-optical module, occurring when an electric current flows across the nonlinear-optical waveguide.
Wherewith, the precision of positioning and mounting the second nonlinear-optical module relative to the first nonlinear-optical module is additionally checked by comparing the power of optical radiation of the laser and/or of the laser module and/or of the first nonlinear-optical module transmitted through the second nonlinear-optical module in the absence of electric current flowing across the nonlinear-optical waveguide of the second nonlinear-optical module and when current flows across it.
During the assembly, as a rule, the optical elements of the nonlinear-optical module and the nonlinear-optical modules are connected by means of fiber-optic connectors with physical. contact, optical fiber sockets, connecting sockets, splices. Optical isolators in the form of optical waveguides, usually as fiber-optic isolators, can be placed between the optical elements and/or before the nonlinear-optical module input and/or after its output and/or between the nonlinear-optical modules.
The object is also achieved in a device for processing optical signals, including at least two optical modules, each of which contains one or two nonlinear-optical waveguide(s) made on the basis of a layered semiconductor MQW-type structure with alternating layers containing at least two hetero-transitions, and a nonlinear-optical waveguide made with the possibility of propagation of two UDCWs in it, and the outputs and inputs of the optical modules are connected to each other in a circuit appropriate to the function of processing the optical signal, wherewith the nonlinear-optical waveguide is supplied with electrical contacts for passage of electric current through them, the outputs and inputs of the preceding and subsequent optical modules are mounted relative to each other with a precision provided by positioning them with use of the luminescent radiation of the nonlinear-optical waveguide of the preceding and/or subsequent nonlinear-optical module, occurring when electric current flows through the nonlinear-optical waveguide.
As a rule, the output/input elements of optical modules, appropriate outputs and inputs of which are optically connected, are made as optical waveguides and are connected by splice or by optical connectors.